Valve mechanisms

ABSTRACT

An apparatus for regulating fuel consumption of an internal combustion engine. A valve mechanism forms a part of the connecting linkage between the throttle pedal and a fuel consumption regulating mechanism. Fluid impulses are provided by opening and closing passages through the valve mechanism in response to movement of the throttle pedal and the throttle linkage. Such a valve mechanism may include first and second valve passages, a valve means for placing each of these passages in an open condition or closed condition wherein a biasing force is exerted on the valve means for placing the passages in one of said conditions and an actuating member is provided for displacing the valve means against the biasing force such that in a first position of the actuating member, the first passage is open and the second passage is closed and in a second position of the actuating member the first and second passages are closed and in a third position of the actuating member the second passage is open and the first passage is closed. The elements are arranged such that the force required to displace the actuating member from the second position to the third position is greater than the force required to displace the actuating member from the first position to the second position.

United States Patent [72] Inventor Karl Gustav Ahlen Stockholm, Sweden 21 AppLNo. 795,947

[22] Filed Feb. 3, 1969 [45] Patented Mar. 9, 1971 [73] Assignee S.R.M.Hydromekanik AB Stockholm-Vallingby, Sweden [32] Priority Feb. 7, 1968 [3 3] Great Britain [3 l 6062/68 [54] VALVE MECHANISMS (inquired); 137/595, 596, 625.69, (inquired); 74/843, (Inquired) [56] References Cited UNITED STATES PATENTS 2,841,129 7/1958 Reggio l23/l39.l7X 2,910,057 10/1959 Suttle 123/l39.18UX

2,920,499 1/ l 960 Hobbs ABSTRACT: An apparatus for regulating fuel consumption of an internal combustion engine. A valve mechanism forms a part of the connecting linkage between the throttle pedal and a fuel consumption regulating mechanism. Fluid impulses are provided by opening and closing passages through the valve mechanism in response to movement of the throttle pedal and the throttle linkage. Such a valve mechanism may include first and second valve passages, a valve means for placing each of these passages in an open condition or closed condition wherein a biasing force is exerted on the valve means for placing the passages in one of said conditions and an actuating member is provided for displacing the valve means against the biasing force such that in a first position of the actuating member, the first passage is open and the second passage is closed and in a second position of the actuating member the first and second passages are closed and in a third position of the actuating member the second passage is open and the first passage is closed. The elements are arranged such that the force required to displace the actuating member from the second position to the third position is greater than the force required to displace the actuating member from the first position to the second position.

PATENTED m 9l97l SHEET 2 [IF 4 m GI VALVE MlEClilANiSMS This invention relates to valve mechanisms. A valve mechanism in accordance with this invention may be used to provide an output impulse or other signal for controlling the operation of additional equipment and particularly for controlling mechanical and hydromechanical transmissions for motor vehicles.

For many years there has been a need for indicating the zero throttle position and the so called kickdown throttle position, that is the position in which the throttle is fully depressed. Hitherto electrical contacts and valves have been used for providing impulses or signals in the zero throttle and kickdown positions. Known valves have been connected with the throttle pedal, the carburetor or the fuel injection pump depending upon the form of engine regulator mechanism used. Where such valves have been used for heavy vehicles, the valves have always been dependent for-their operation upon a very high external force and this force has been reflected in the force necessary to depress tlie throttle pedal from zero to maximum positions. In an attempt to reduce the force necessary to depress the throttle and operate the known valves, it was proposed to use a manually operable device for providing the necessary impulses.

It is an object of thepresent invention to appreciably reduce the force required to operate a valve system and produce the necessary impulses by operation of the throttle pedal without subjecting the driver'of a vehicle to unnecessary strain.

According to one feature of the invention a valve mechanism for producing impulses responsive to the movement of an engine throttle pedal forms a part of a connecting linkage between the throttle pedal and a regulating mechanism of the engine.

According to a further feature of the invention the valve mechanism comprises first and second valves each having a valve member movable between open and closed positions against a force urging the member into one of the said positions, and an actuating member displaceable against a biasing force so that, in a first position of the actuating member the first valve is open and the second valve is closed, in a second position of the actuating member the first and second valves are closed and in a third position of the actuating member the second valve is open and the first valve is closed, the force required to displace the actuating member from the second position to the third position being greater than the force required to displace the actuating member from the first position to the second position.

Several forms of valve mechanism in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which:

FiG. 1 shows diagrammatically a layout of an automatic transmission employing a valve mechanism in accordance with the invention;

H6. 2 shows a longitudinal section through a valve mechanism of the invention;

MG. 3 is a section taken on line 3-3 of FIG. 2;

PEG. 4 shows a longitudinal section through a modified valve mechanism;

MG. 5 is a section on the line V-V of FIG. 4;

FEG. 6 is an end elevation of the device shown in FIG. 4;

MG. '7 shows a longitudinal axial section through a further modified valve mechanism; and

FIG. 8 is section on the line VIII-VIII of FIG. 7.

in FIG. l a hydraulic transmission 2 is mounted on an engine having a fuel injection pump 6 and a connecting linkage generally indicated at 8 to a throttle pedal (not shown). A valve mechanism 16 according to the invention is mounted as shown to form part of the throttle pedal connecting linkage. A pressure air line l2 serves to connect the valve mechanism to the pressure air system of the vehicle and additional pressure connections M and 16 serve to transmit impulses from the valve mechanism in dependence on the position of the throttle pedal.

In the particular case described the transmission is a SRM DS transmission and the pipe 14 carries pressure air when the throttle pedal is released thereby giving an impulse in the transmission and releasing the guide vane for free rotation this position in such transmissions being termed positive neutral." This means that if reverse gear is also released the transmission is freely rotatable. It also means that should reverse gear be engaged there is no torque multiplication through the transmission and consequently there is no tendency for a creeping condition to be realized. Such a creeping condition is otherwise very great since the transmission in question has a 9:1 torque ratio. When the throttle pedal is fully depressed into its bottom position which generally speaking is beyond the position of full throttle or maximum fuel injection, the valve mechanism as shown in FIG. 2 conveys pressure air through pipe 16 to control the transmission in such a way that in a particular field direct drive is released enabling maximum tractive effort to be obtained at the expense of a slight fall in fuel economy. This last mentioned position is, as previously indicated, referred to as the kickdown throttle position.

Reference was made earlier to a reduction in the force necessary to operate a valve mechanism in accordance with this invention and this is due to the fact that a return spring 18 (FIG. 1) placed on the connecting rod on the fuel injection pump side of the valve mechanism 10 provides the return force. No other spring force is required and it is not necessary for the spring 18 to be any stronger than a normal fuel injection pump return spring because the only additional forces with which the return spring has to contend are those arising from the connection of the U-shaped and flexible pressure lines 12, 14 and I6 and such forces are minimal.

Referring to FIGS. 2 and 3 which show the valve mechanism in detail an actuating member 30 having a threaded end 30A for mounting in the linkage leading to the throttle pedal, is slidable in a casing 32. A threaded bore 32A in the casing provides for the connection of the casing in the throttle pedal linkage to the fuel injection pump or throttle. Located between the actuating member 30 and the casing 32 are two helical springs 34 and 36. The spring 34 acts against a flange 38 carried by the actuating member 30 and the spring 36 acts against a ring 40 slidable within the casing 32. The position of the ring 40 in a direction to the right as viewed in FIG. 2 is limited by a stop ring 31A carried by the casing 32.

The spring 34 serves to retain the member 32 in its extended position wherein a valve 4l2 is maintained open under the influence of a projection 44 carried by the actuating member 30. The projection 44 cooperates with a pin 46 carried by a valve plate 48 tending under normal conditions to close a bore 52 under the influence of a spring 50. Pressure air from the vehicle pressure air system enters the valve mechanism through inlet 54 and when the bore is open passes through the bore 52 into a passage 56 and thence to pipe 14 (FIG. 1).

The valve plate 48 comprises a metal ring carrying a disc made from rubber or other flexible material and when the bore 52 is open, the valve 42 closes an outlet 59 from chamber 60. Since the spring 34 is weaker than the return spring 18 very little, if any, additional force is required to depress the throttle and cause actuation of the valve assembly 46, 48, 59.

When a driver depresses the throttle pedal, initial movement of the pedal will compress the spring 34 and the flange 36 will abut against the ring 40 normally retained in a position by spring 36 to maintain the valves 42 and 5% closed. In this position the valve actuating mechanism transmits a force from the primary side (pedal) to the secondary side (pump arm) and serves only to vary the position of the arm of the fuel injection pump until the return spring 18 is in its maximum compressed position and the fuel injection pump regulating arm is consequently in the maximum fuel injection position. In this position the casing 32 is prevented from further axial movement. Additional pressure on the throttle pedal will then cause the spring 36 to be compressed which results in valve 58 being opened and pressure air conveyed (in the same way as for valve 42) but to the pipe 16 thereby transmitting the required impulse to the transmission. This impulse disconnects direct drive as soon as higher tractive effort is obtainable from the hydraulic transmission.

The force of the spring 36 may be chosen to be independent of the spring 18 and is sufficiently strong to enable a driver to feel a distinct difference between maximum fuel injection and kickdown positions.

The pipes 12, 14 and 16 are as mentioned above flexible and these assume a U-shape i.e. bent through 180 between the valve mechanism 10 and a stationary abutment on the engine. This arrangement means that the transverse dimension measured between the generally parallel sides of the U-shaped pipes remains substantially constant during actual movement of the valve mechanism 10 and little or no additional force is applied to the valve mechanism 10 by the pipe connections.

A valve mechanism in accordance with the invention has the advantage that it is independent of any movement of the vehicle cabin or any changes in dimensions of the throttle connecting linkage. The valve mechanism may be assembled into the throttle pedal linkage before delivery of the transmission enabling testing in situ and setting of the valve mechanism to be carried out prior to delivery which apart from the features already mentioned concerning the reduction of force required to operate the throttle pedal by the driver offers considerable improvement over known devices.

A modification of the valve mechanism 10 is shown in FIGS.

4 to 6. In this construction a casing 61 carries within the same a slidable actuating member 62, the casing 61 and member 62 being connected in the throttle pedal linkage, depression of the pedal moving the member 62 in the direction of the arrow P. Disposed between casing 61 and member 62 are two compression springs 64, 65, the inner weaker spring 64 acting between an abutment 66 held by stops 67 on the casing 61 and a movable ring 74 slidable on the member 62 and limited as to its inward movement by a stop 68 secured to the member 62. The outer spring 65 acts between the abutment 66 and a ring 69 slidable on the casing 61 and limited as to its inward movement by a shoulder 70 on the casing. Arranged at the opposite end of the casing 61 is an axially slidable valve 71 of the piston type having sections of different diameters for opening and closing passages across a plurality of rings 72 mounted in a valve casing 73. Formed in the easing 73 are a number of radial passages three of which communicate respectively with the openings to which the pressure pipes 14, 54, 16 are connected through bores 75, 76, 77 respectively. The valve 71 is connected to the movable member 62 by a coupling disc which allows lost motion between the members 62 and 71. The member 62 is supported in the casing 61 by bearings 63.

As shown in FIG. the casing 61 and the valve casing 73 are interconnected by a number of bolts 79. The casing 61 is lubricated and is maintained oil tight by a flexible sealing ring 80 ofrubber or the like.

In operation in the case of zero throttle with the member 62 held in its left-hand position as shown in FIGS. 4 and 5 by the spring 64, the position of the valve 71 is such that pressure air entering through connection 54 and bore 76 is directed through bore 75 and pipe 14 for the connection of the positive neutral of the transmission. Depression of the throttle pedal moves member 62 to the right relative to casing 61 compressing spring 64, while the valve 71 at first remains stationary due to the lost motion connection with member 62. Continued movement of member 62 then moves valve 71 to the right, thereby breaking the communication between bores 76 and 75 and venting bore 75 to atmosphere through the valve. The spring 64 is so weak that the compression thereof does not produce a force between the members 61 and 62 sufficient to move the regulating arm of the injection pump.

Further movement of the members 62 and 71 to the right causes the movable ring 74 on the member 62 to contact the ring 69, the member 62 moving the arm of the injection pump to full throttle position and then compressing spring 65 moving further to kickdown position at which point the valve member 71 has moved to the right sufficiently to provide communication between the bores 76 and 77 so that pressure air passes from the supply opening 54 to the pipe 16 and effects the kickdown at the transmission.

The provision of the lost motion connection between the member 62 and the valve 71 enables the position of the throttle or regulating arm of the injection pump to remain steady in the case where the driver, due to bad road conditions or the like, cannot hold the throttle pedal steady, so that hunting" will not arise.

FIGS. 7 and 8 show a modification of the valve mechanism of FIGS. 4 to 6 which is particularly adapted for heavy off-theroad vehicles. In this case the operating mechanism 61, 62 of the control valve 71 is the same as that described with reference to FIGS. 4 and 5. The operation of the valve 71 is however such that pressure air passing through the valve is not led directly to the transmission to provide the necessary impulse but through servovalves 82, 92 shown in FIG. 8. This has the advantage that the setting for positive neutral or for kickdown is effected practically immediately through large areas when the respective servovalve is actuated for the setting.

The servovalves 82, 92 are of the piston type having sections of differing diameters for opening and closing passages across a plurality of O-rings 83 and 84 respectively. The servo valve 82 has in its casing apertures which communicate under control of the control valve 71 at 85 with the pressure air supply at 86 with the positive neutral of the transmission through pipe 14 and at 87 with the atmosphere. Similarly the casing of the servo valve 92 is provided with apertures 88, 89, 90 communicating respectively with the pressure air supply, with the kickdown of the transmission through pipe 16 and with the atmosphere.

The valve assembly is mounted in the linkage of the throttle pedal so that, on depression of the pedal, the member 62 moves to the right as shown by the arrow R in FIG. 8. In the neutral position of the pedal the elements of the control valve and servovalves will be in the positions shown in FIG. 8. At this time pressure air is conveyed from the air supply through 54 through the passage 76, valve 71 and opening 75 to the lefthand end face of the servovalve 82 thereby pressing the servovalve 82 to the right against the force of a spring 91. In this position of the piston 82, a passage having a large area leads pressure air from aperture 85 to aperture 86, thus causing connection of the positive neutral of the transmission through pipe 14.

When the throttle pedal is depressed, the valve member 71 is moved to the right closing the connection between the passage 76 and the opening 75 and venting the latter to the atmosphere at 94 thus causing air at the left hand end face of the piston 82 to vent to atmosphere. Thus the spring 91 presses the piston 82 to the left thereby venting air through 86 from the neutral and disconnecting positive neutral. Initial movement of the valve member 71 and compression of the spring 64 is stopped by abutment against the prestressed spring 65.

Further depression of the throttle pedal merely moves the arm of the fuel injection pump to increase the speed of the engine. When the said arm reaches its end position compression of the two springs 64 and 65 will move the valve member 71 further to the right allowing pressure air to pass from 54 to the opening 77 and then to the left hand end face of the servovalve 92 thereby displacing the piston 92 to the right against the force of a spring 93. This movement of the piston 92 allows air to pass through a large area from the opening 77 to the aperture 89 thereby efiecting connection of kickdown in the transmission through the pipe 16.

When the throttle pedal is released, the whole sequence of operation will follow in the reverse order. In this embodiment also, lost motion is provided between the member 62 and the control valve 71, to avoid hunting.

Iclaim:

1. In combination, a combustion engine, a regulating mechanism for regulating the fuel consumption of the engine,

a throttle pedal, a connecting linkage connecting the throttle pedal to the regulating mechanism to operate the same to regulate the fuel consumption of the engine, and a valve mechanism, fluid passages through the valve mechanism for passing fiuid for producing fluid impulses, said passages being opened and closed in response to movement of the throttle pedal and the connecting linkage, said valve mechanism forming a part of said connecting linkage between the throttle pedal and the regulating mechanism for movement therewith.

2. The invention of claim 1, including a hydraulic transmission means operatively connected to the engine, said valve mechanism being operatively connected to the said transmission to operate the transmission by said impulses.

3. The invention of claim ll, wherein said passages include first and second valve passages, valve means for placing each of said passages in an open condition or a closed condition, means for exerting a biasing force on the valve means for placing the passages in one of said conditions and an actuating member for displacing said valve means against said biasing force so that, in a first position of the actuating member the first valve passage is open and the second valve passage is closed, in a second position of the actuating member the first and second valve passages are closed and in a third position of the actuating member the second valve passage is open and the first valve passage is closed, the force required to displace the actuating member from the second position to the third position being greater than the force required to displace the actuating member from the first position to the second position.

d. A combination according to claim 3 wherein the valve means is enclosed in a casing and wherein the displaceable actuating member is connected to one part of the connecting linkage and said casing is connected to another part of said linkage.

5. A combination according to claim 3 wherein the first position of the actuating member corresponds to zero throttle and the first valve passage is then open to provide a fluid impulse, and wherein initial displacement of the actuating member closes said first valve passage without influencing the said engine regulating mechanism.

ii. A combination according to claim 3 wherein a lost-motion device is included in the connection between the actuating member and the valve means.

7. A combination according to claim 3 including a transmission operatively connected to said engine, and wherein movement of the throttle linkage effects the setting of said transmission by means of fluid impulses which causes air to be supplied to or vented from said transmission through said first and second passages.

d. A combination according to claim 3 wherein the movement of the throttle linkage comprises an initial movement changing the position of the first valve passage, a second movement during which the valve means transfers said movement of the throttle linkage to the said regulating mechanism without changing the position of the first or second valve passages and a final movement wherein the force in the linkage exceeds a predetermined value and changes the position of the second valve passage.

9. A combination according to claim 3 wherein the valve means comprises separate valve members operated individually by the said actuating member.

iii). A combination according to claim 9 including a casing, first and second chambers in said casing, first and second passages leading from the first and second chambers, respectively, to a source of pressure fluid, one of said valve members in each chamber, a spring means urging each valve member to close its respective passage and also to open an aperture from its respective chamber to atmosphere, and said actuating member being operable during its first and third positions to move the valve members of the first and second chambers, respectively, to open the first and second passages, respectively.

ll. A combination according to claim 3 wherein the valve means comprises axially spaced parts of a common piston type valve member having sections of different diameter for opening and closing the said passages.

12. A combination according to claim 11 wherein the casing surrounding the said valve member is formed with channels for the passage of air, separated by O-rings of elastic material, said channels being arranged to intercommunicate by axial displacement of the piston type valve member, and said channels including said first and second passages, a pressure fluid supply channel and a vent channel.

13. A combination according to claim 12, including a transmission operatively connected to said engine, and wherein movement of the throttle linkage effects the setting of said transmission by means of said impulses which causes air to be supplied to or vented from said transmission through said first and second passages, and wherein intercommunication of the supply channel and the first channel leads pressure air to one member of the transmission and intercommunication of the supply channel and the third channel leads pressure air to another member of the transmission. 7

14. A combination according to claim 13 including a servovalve interposed in each path of flow of pressure air from the valve member to the respective transmission member, said servovalves forming large flow areas, whereby immediate setting of said transmission members is obtained.

15. A combination according to claim 11 including a relatively weak spring urging the valve member to the first position, and wherein the actuating member is operatively connected to the valve member by a lost-motion device and wherein the actuating member moves, on actuation of the throttle pedal, against the force of said weak spring to change the position of the first valve passage and subsequently move as a unit with the valve casing to actuate the regulating mechanism of the engine.

16. A combination according to claim 15 including an additional spring, stronger than said relatively weak spring, and wherein the actuating member, on reaching the end position of the regulating mechanism, is movable further against said. additional spring pressure to change the position of the second valve passage.

17. A combination according to claim 3 wherein the actuating member is supported in an external casing by roller bearings.

18. A combination according to claim 3 wherein the movement into the third position of the actuating member to open the second valve passage takes place under a higher pressure than that necessary to move the said regulating mechanism to its maximum limiting position and corresponds to kickdown position of the said throttle.

19. A combination according to claim 3 having connections for flow of pressure fluid to and from the valve mechanism, said connections comprising U-shaped flexible pipes having the legs of the U-shaped flexible pipes having the legs of the U extending substantially parallel to the direction of displacement of the actuating member.

20. A valve mechanism having fluid passages, means for producing fluid impulses through the passages, said valve mechanism comprising first and second valve passages, a valve means for placing each of said passages in an open condition or a closed position, means for exerting a biasing force on the valve means for placing the passages in one of said conditions and an actuating member for displacing said valve means against said biasing force so that, in a first position of the actuating member the first valve passage is open and the second valve passage is closed, in a second position of the actuating member the first and second valve passages are closed and in a third position of the actuating member the second valve passage is open and the first valve passage is closed, the force required to displace the actuating member from the second position to the third position being greater than the force required to displace the actuating member from the first position to the second position.

21. A valve mechanism according to claim 20, wherein a lost-motion device is included in the connection between the actuating member and the valve means.

22. A valve mechanism according to claim 20, wherein the valve means comprises separate valve members operated individually by the said actuating member.

23. A valve mechanism according to claim 22, including a casing, first and second chambers in said casing, first and second passages leading from the first and second chambers, respectively, to a source of pressure fluid, one of said valve members in each chamber, a spring means urging each valve member to close its respective passage and also to open an aperture from its respective chamber to atmosphere, and said actuating member being operable during its first and third positions to move the valve members of the first and second chambers, respectively, to open the first and second passages respectively.

24. A valve mechanism according to claim 20, wherein the valve means comprises axially spaced parts of a common piston type valve member having sections of different diameters for opening and closing the said passages.

25. A valve mechanism according to claim 24, wherein the casing surrounding the said valve member is formed with channels for the passage of air, separated by O-rings of elastic material, said channels being arranged to intercommunicate by axial displacement of the piston type valve member, and said channels including said first and second passages, a pressure fluid supply channel and a vent channel.

26. A valve mechanism according to claim 20, wherein the movement into the third position of the actuating member to open the second valve passage takes place under a higher pressure than that necessary to move the said regulating mechanism to its maximum limiting position and corresponds to kickdown position of the said throttle. 

1. In combination, a combustion engine, a regulating mechanism for regulating the fuel consumption of the engine, a throttle pedal, a connecting linkage connecting the throttle pedal to the regulating mechanism to operate the same to regulate the fuel consumption of the engine, and a valve mechanism, fluid passages through the valve mechanism for passing fluid for producing fluid impulses, said passages being opened and closed in response to movement of the throttle pedal and the connecting linkage, said valve mechanism forming a part of said connecting linkage between the throttle pedal and the regulating mechanism for movement therewith.
 2. The invention of claim 1, including a hydraulic transmission means operatively connected to the engine, said valve mechanism being operatively connected to the said transmission to operate the transmission by said impulses.
 3. The invention of claim 1, wherein said passages include first and second valve passages, valve means for placing each of said passages in an open condition or a closed condition, means for exerting a biasing force on the valve means for placing the passages in one of said conditions and an actuating member for displacing said valve means against said biasing force so that, in a first position of the actuating member the first valve passage is open and the second valve passage is closed, in a second position of the actuating member the first and second valve passages are closed and in a third position of the actuating member the second valve pAssage is open and the first valve passage is closed, the force required to displace the actuating member from the second position to the third position being greater than the force required to displace the actuating member from the first position to the second position.
 4. A combination according to claim 3 wherein the valve means is enclosed in a casing and wherein the displaceable actuating member is connected to one part of the connecting linkage and said casing is connected to another part of said linkage.
 5. A combination according to claim 3 wherein the first position of the actuating member corresponds to zero throttle and the first valve passage is then open to provide a fluid impulse, and wherein initial displacement of the actuating member closes said first valve passage without influencing the said engine regulating mechanism.
 6. A combination according to claim 3 wherein a lost-motion device is included in the connection between the actuating member and the valve means.
 7. A combination according to claim 3 including a transmission operatively connected to said engine, and wherein movement of the throttle linkage effects the setting of said transmission by means of fluid impulses which causes air to be supplied to or vented from said transmission through said first and second passages.
 8. A combination according to claim 3 wherein the movement of the throttle linkage comprises an initial movement changing the position of the first valve passage, a second movement during which the valve means transfers said movement of the throttle linkage to the said regulating mechanism without changing the position of the first or second valve passages and a final movement wherein the force in the linkage exceeds a predetermined value and changes the position of the second valve passage.
 9. A combination according to claim 3 wherein the valve means comprises separate valve members operated individually by the said actuating member.
 10. A combination according to claim 9 including a casing, first and second chambers in said casing, first and second passages leading from the first and second chambers, respectively, to a source of pressure fluid, one of said valve members in each chamber, a spring means urging each valve member to close its respective passage and also to open an aperture from its respective chamber to atmosphere, and said actuating member being operable during its first and third positions to move the valve members of the first and second chambers, respectively, to open the first and second passages, respectively.
 11. A combination according to claim 3 wherein the valve means comprises axially spaced parts of a common piston type valve member having sections of different diameter for opening and closing the said passages.
 12. A combination according to claim 11 wherein the casing surrounding the said valve member is formed with channels for the passage of air, separated by O-rings of elastic material, said channels being arranged to intercommunicate by axial displacement of the piston type valve member, and said channels including said first and second passages, a pressure fluid supply channel and a vent channel.
 13. A combination according to claim 12, including a transmission operatively connected to said engine, and wherein movement of the throttle linkage effects the setting of said transmission by means of said impulses which causes air to be supplied to or vented from said transmission through said first and second passages, and wherein intercommunication of the supply channel and the first channel leads pressure air to one member of the transmission and intercommunication of the supply channel and the third channel leads pressure air to another member of the transmission.
 14. A combination according to claim 13 including a servovalve interposed in each path of flow of pressure air from the valve member to the respective transmission member, said servovalves forming large flow areas, whereby immediate setting of said tranSmission members is obtained.
 15. A combination according to claim 11 including a relatively weak spring urging the valve member to the first position, and wherein the actuating member is operatively connected to the valve member by a lost-motion device and wherein the actuating member moves, on actuation of the throttle pedal, against the force of said weak spring to change the position of the first valve passage and subsequently move as a unit with the valve casing to actuate the regulating mechanism of the engine.
 16. A combination according to claim 15 including an additional spring, stronger than said relatively weak spring, and wherein the actuating member, on reaching the end position of the regulating mechanism, is movable further against said additional spring pressure to change the position of the second valve passage.
 17. A combination according to claim 3 wherein the actuating member is supported in an external casing by roller bearings.
 18. A combination according to claim 3 wherein the movement into the third position of the actuating member to open the second valve passage takes place under a higher pressure than that necessary to move the said regulating mechanism to its maximum limiting position and corresponds to kickdown position of the said throttle.
 19. A combination according to claim 3 having connections for flow of pressure fluid to and from the valve mechanism, said connections comprising U-shaped flexible pipes having the legs of the U-shaped flexible pipes having the legs of the U extending substantially parallel to the direction of displacement of the actuating member.
 20. A valve mechanism having fluid passages, means for producing fluid impulses through the passages, said valve mechanism comprising first and second valve passages, a valve means for placing each of said passages in an open condition or a closed position, means for exerting a biasing force on the valve means for placing the passages in one of said conditions and an actuating member for displacing said valve means against said biasing force so that, in a first position of the actuating member the first valve passage is open and the second valve passage is closed, in a second position of the actuating member the first and second valve passages are closed and in a third position of the actuating member the second valve passage is open and the first valve passage is closed, the force required to displace the actuating member from the second position to the third position being greater than the force required to displace the actuating member from the first position to the second position.
 21. A valve mechanism according to claim 20, wherein a lost-motion device is included in the connection between the actuating member and the valve means.
 22. A valve mechanism according to claim 20, wherein the valve means comprises separate valve members operated individually by the said actuating member.
 23. A valve mechanism according to claim 22, including a casing, first and second chambers in said casing, first and second passages leading from the first and second chambers, respectively, to a source of pressure fluid, one of said valve members in each chamber, a spring means urging each valve member to close its respective passage and also to open an aperture from its respective chamber to atmosphere, and said actuating member being operable during its first and third positions to move the valve members of the first and second chambers, respectively, to open the first and second passages respectively.
 24. A valve mechanism according to claim 20, wherein the valve means comprises axially spaced parts of a common piston type valve member having sections of different diameters for opening and closing the said passages.
 25. A valve mechanism according to claim 24, wherein the casing surrounding the said valve member is formed with channels for the passage of air, separated by O-rings of elastic material, said channels being arranged to intercommunicate by axial dispLacement of the piston type valve member, and said channels including said first and second passages, a pressure fluid supply channel and a vent channel.
 26. A valve mechanism according to claim 20, wherein the movement into the third position of the actuating member to open the second valve passage takes place under a higher pressure than that necessary to move the said regulating mechanism to its maximum limiting position and corresponds to kickdown position of the said throttle. 